The Effects of Vegetable Preloading on Postprandial Glycemia, Insulinaemia and Gastric Emptying

The proposed research is part of strategies to manipulate postprandial glycemia and generate weight-control-related benefits, such as promoting satiation. Literature has shown pre-loading caloric nutrients can change postprandial glycemia, but the mechanism is unclear. The investigators hypothesize that a small number of nutrients released in the small intestine can initiate physiological changes and develop feedback control to delay gastric emptying, leading to the delay in digestion of glycemic carbohydrates and the consequent moderate glycemic responses. The investigators propose to use potatoes as the testing glycemic carbohydrates, and the pre-load foods are green vegetables. The investigators will be testing the optimal preload time to achieve the highest control of glycemic response as well as the strongest effect in satiety induction. In addition, green vegetables will be consumed with or without a preload fat enhancer (canola oil) to investigate the mechanism behind significant preload compositions. Healthy adults will be instructed to eat the leafy vegetables first (with or without canola oil), followed by the potato foods (i.e., mashed potatoes). The measurement is the gastric emptying time, blood sugar concentration, insulin, and an appetite-related gut hormone GLP-1. In order to monitor gastric emptying using a non-invasive approach, a popular breath test used in children and a hydrogen breath test will be used to present the change of gastric emptying and the level of gut fermentation.

Results will demonstrate the mechanism of the impact of pre-loading nutrients on the digestion of glycemic carbohydrates. The goal is to eliminate the negative influence of glycemic carbohydrate consumption. Instead, to generate health benefits from dietary carbohydrates.

Inclusion criteria

• Normal body mass index (18.5 kg/m2 to 24.9 kg/m2), weight >/= 45 kg
• Normal blood pressure </=120/80 mmH
• Fasting blood glucose of <5.6 mmol/l
• Able to provide written informed consent before participating in the study.
• Able to communicate adequately to comply with the requirements of the entire study, i.e., able to eat test meal and provide breath samples.

Exclusion criteria

• Smokers.
• Individuals with any metabolic diseases (such as diabetes, hypertension etc).
• Individuals with known glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency).
• Individuals with medical conditions and/or taking medications known to affect glycaemia (glucocorticoids, thyroid hormones, thiazide diuretics).
• Individuals who take any prescribed medication or dietary supplements which may interfere with the study measurements.
• Individuals who have any major organ dysfunction (eg. cardiovascular, respiratory, hepatic, renal, gastrointestinal) that may influence taste, olfaction, appetite, digestion, metabolism, absorption or elimination of test foods, nutraceutical or drug.
• Individuals with history of malabsorption due to mucosal disease, pancreatic disease, or other causes.
• Individuals with history of gastrointestinal disease or surgery (excludes appendectomy, hernia repair and anorectal disorders).
• Individuals who are allergic/intolerant to any of the test foods to be administered, or any of the following common food and ingredients: eggs, fish, milk, peanuts, tree nuts, shellfish, soya, wheat, gluten, cereal, fruits, dairy products, meat, vegetable, sugar and sweetener, natural food colourings or flavourings, sulphites etc.
• People who intentionally restrict food intake.
• People who consume excessive 13C rich products such as corn, sugar beet and pineapple.
• Individuals who partake in sports at the competitive and/or endurance levels
• Individuals who have any known chronic infection or known to suffer from or have previously suffered from or is a carrier of Hepatitis B Virus (HBV), Hepatitis C Virus (HCV), Human Immunodeficiency Virus (HIV).
• Individuals who is a study team member or an immediate family of any study team member.
• Individuals who consume Excessive alcohol: consuming >/= 6 alcoholic drinks per week.